Stress relief



United States Patent STRESS RELIEF Frank K. Fellows and David A. Bell,Killen, Tex.

Application November 10, 1955, Serial No. 546,122

4 Claims. (Cl. 219-50) This invention relates to a method of andapparatus for relieving or overcoming stress in pipe, vessels, towers,manifolds, and the like.

The object of the invention is to provide a method of and-apparatus forremoving stresses or brittleness in metal members while the metalmembers are in situ.

Another object of the invention is to provide a method of and apparatusfor relieving stress in various metal members whereby the operation canbe accomplished without the necessity of removing the member from itsnormal or service position, the method utilizing an introduction ofpower from welding machines so that stress or brittleness can berelieved in the members with a minimum cost and minimum time loss forthe equipment.

A further object of the invention is to provide a method of andapparatus for relieving stress in various metal members which isextremely simple and inexpensive to manufacture and operate.

Other objects and advantages will be apparent during the course of thefollowing description.

In the accompanying drawings, forming a part of this application, and inwhich like numerals are used to designate like parts throughout thesame.

Figure 1 is an elevational view illustrating a metal member such as avessel or tower and illustrating the present invention applied thereto.

Figure 2 is an elevational view illustrating the use of the presentinvention for annealing for removing stress in Welded pipe, tubing orthe like, and with parts broken away and in sections.

Figure 3 is a diagram illustrating the temperature and time foraccomplishing the annealing.

Figure 4 is a side elevational view of one of the insulated supportmembers for the wires.

Figure 5 is a top plan view of the support member of Figure 4.

Figure 6 is a fragmentary view illustrating the insulated bead or bodymembers mounted on a conductor wire.

Figure 7 is a plan view illustrating one of the insulated blocks withthe buss bars mounted therein.

Figure 8 is a sectional View taken on the line 8-8 of Figure 7.

Referring in detail to the drawings, the numeral 10 designates a tower,vessel, manifold or the like which is adapted to be treated by themethod of and apparatus of the present invention. It is to be understoodthat the method of the present invention can be used on other equipmentbesides the tower 10, as for example, the present invention can be usedto relieve stress in welded pipes of tubings indicated by the numeral11, in Figure 2. In Figure 2 the numeral 12 designates the welded jointsbetween the pipes or tubes 11.

The present invention utilizes a plurality of insulated blocks which areeach indicated by the numeral 14, Figure 8, and the blocks 14 may bemade of any suitable material such as porcelain. Each of the blocks 14includes a body portion 15 which is provided with a pair of spacedparallel longitudinally extending recesses or channels 16 which definetherebetween a partition 17. A conductive buss bar 18 is secured withineach of the recesses 16, and extending outwardly from each of the bars18 is a plurality of terminals or bolts 19. Those terminals at the endsof the bars 18 are indicated by the numeral 20.

There is further provided a plurality of conductors 21 which are adaptedto be trained or wrapped around the member 10 or 11 being heat treated,and the conductors 21 have their ends connected to the terminals 19. Aplurality of insulated beads or body members 22 are mounted on theconductors 21, and the body members 22 may be provided with apertures oropenings 23 for the projection therethrough of the conductors 21. Thebody members 22 serve to insulate or maintain the con ductors 21 out ofelectrical contact with the metal member 10 or 11 being treated.

Certain of the terminals 19 on the bars 18 may be interconnectedtogether by bridge wires 24, Figure 7.

There is further provided a means for maintaining a record of thetemperature of the member 10 or 11 being treated, and this meanscomprises contacts or terminals 25 which are arranged contiguous to themember 10 or 11 and these contacts 25 may be secured in place by anysuitable manner and may be of conventional construction. Wires 26 leadfrom the contacts 25 to a suitable conventional thermocouple pyrometer.Thus, an accurate recording of the temperature of the member 10 or 11will be provided. Wires 27 lead from the end terminals 20 on the bars18, and the wires 27 are adapted to be connected to a conventionalwelding machine. Thus, when the welding machine is actuated orenergized, electrical current will flow from the wires 27 through thebars 18 and then the Wires 21 will be heated or caused to glow due tothe electrical energy passing therethrough and this heat from the wires21 will heat the member 10 or 11 being treated so that the stress in themetal will be relieved or overcome. The stress in the members 10 and 11usually result after the members have been in service for long periodsor active periods of time.

Referring to Figures 4 and 5 of the drawings, there is shown anaccessory which may be used for helping to maintain the wires 21 out ofcontact with the members 10 or 11. Thus, in Figures 4 and 5 the numeral28 designates a support member which can be made of any suitableelectrically insulated material such as porcelain, and the supportmember 28 may be provided with a plurality of spaced parallel notches orrecesses 29 for receiving therein portions of the wires 21.

Fromthe foregoing, it is apparent that there has been provided a methodof 'and apparatus for use in relieving stress in various members such astowers, vessels, manifolds, pipes and the like. In Figure l theapparatus is shown mounted on a tower or vessel 10 and in Figure 2 theapparatus is shown mounted on welded pipe or tubing 11. Thus, with theapparatus arranged as shown in Figure l, a plunality of the blocks 14are arranged so that their longitudinal axis extends parallel to thelongitudinal axis of the member 19 and these blocks 14 have their endsspaced slightly apart. The terminals 20 are adapted to be connected to asuitable source of electrical energy as for example to a conventionalwelding machine through the medium of the wires 27. The contacts 25 aremounted on the member 10 in any suitable manner, :and the wires 26 leadfrom the contacts 25 to a suitable conventional thermocouple pyrometer.Thus, when the welding machine is energized, the current will flow fromthe wires 27 to the terminals 20 and then to the bus bars 13. Thiscurrent will then flow up through the terminals 19 and up through thewires 21. These wires 21 will thus be heated and the heat from the wires21 will raise the temperature of the member 10 or memher 11 and byraising the temperature of these members to [the desired degree,brittleness will be removed and also any stress in the members will berelieved since the metal will be annealed. After a given section of themember or 11 has been treated, the blocks 14 can be moved to the nextsection to be treated so that the entire member 19 or 11 can be heattreated with the present invention. The blocks 14 are made of insulatedmaterial so that the bars 18 are electrically insulated from the member10 or member ill. The wires or conductors 21 are also electricallyinsulated from the member 10 or 11 by means of the porcelain bodymembers 22 and also by means of the support members 28 which may be madeof electrically insulating material such as porcelain also. Thus, thesupport members 2@ may be interposed between portions of the wires 21and the member 10 or 11. In Figure 3, there is shown a graph whichillustrates the steps in heat treating the member 10 or 11 so as toeffect the desired annealing. Thus, plotted along the vertical axis isthe temperature in degrees, and plotted along the horizontal axis is thetime that the heat is applied. It will be seen that there results on thescale or graph a recording of the temperatuire in degrees and time thatthe member is exposed to the heat, and this graph may result from thecontacts which are electrically connected to the thermocouple pyrometer.

The welding machine supplies the electrical energy and heat whereby thewires 21 cause the member 1% or 11 to become annealed so that thestresses are relieved or overcome or removed.

In Figure 3 there is shown a typical graph wherein temperature itplotted against time on a recording instrument during the stress reliefof a member treated by the process of the present invention. It is to beunderstood that the temperature and time of treatment will vary fordiiferent types of materials being treated. The members are treated byprogressive stages and the member which may be a tower, vessel, manifoldor the like, is treated in situ so that it does not have to be movedfrom place to place, when being treated. This is specially suitable whenlarge members which are often encountered, are to be treated. Thetreatment is performed in the field without removal of the object to betreated from its normal service position and the treatment uses weldingmachines for power. A plurality of welding machines can be used andafter a given section of a tower or the like has been treated, the wirescan be moved, to a fresh section to be treated and a desired amount ofoverlap in the treatment of the sections may be used. The wires 21 arearranged in parallel on the member being treated. The thermocouples 25are staggered around the entire area being treated so that an accuratereading is brought about. If desired, additional insulation can beplaced where needed and if desired the inside of the member 10 or 11 mayalso be insulated to increase the efiiciency of the operation. Also,small portions of a tower, vessel or the like which have become stressedmay be treated for relief of the stressed area without treating theentire unit. Thus, the present invention will eliminate the costlyprocess of annealing units in a furnace. The arrangement shown in Figure6 provides a flexible arrangement for the wires 12 so that the wires canbe readily wrapped around the member 10 or 11; The wires 24 serve asjumper wires so that there will be a continuous circuit for theelectrical energy. The members are adapted to be heat treated inprogressive stages. The members can be heat treated at a small cost andwith a minimum time loss since it is not necessary to move the equipmentto a furnace.

The members which are treated by the present invention may sufferstresses after they have been in service for a long period of time and:as for example when the members have been exposed to varyingtemperatures or adverse conditions. The arc welding machine or machineswhich apply the electrical energy may have a capacity of'300 ampereswith a 40 or 50 volt capacity.

In use, the tower or other members are taken out of service andpermitted to cool and then cleaned and the stress cracks are weldedalong with any other repairs that may be needed. The wires 21 are thenwrapped on the tower and the plurality of wires 21 are arranged quiteclose together. The number of welding machines connected to theterminals 20 can be varied as desired and the member may be treated inonly one operation or else it can be treated in progressive stages.After the windings are in place and secured and the thermocouples 25 arespaced over the area to be treated, insulation is placed over the areabeing treated and such insulation may be magnesium or asbestos and thisasbestos which is placed over the apparatus has its joints sealed. Ifdesired the inside of the tower may also be insulated. The thermocouplesare connected to the recording instrument and the welding machines arestarted and amperage is adjusted so that the rise in temperature is 400per hour in the metal being treated. This rise is continued until thetemperature for annealing the type or metal being treated has beenreached at which point the amperage of the welding machine is reduced tohold the annealing temperature for such time as specified in A. S. T. M.tables for processing this type of metal. At the end of this specifiedtime, the amperage is further reduced so that there is a cooling rate ofthe metal of 200 per hour or to conform to the cooling rate set forth inthe A. S. T. M. tables for this type of ,metal until the temperaturedrops to 300 at which point the machines may be stopped and removed fromthe line and the metal permitted to cool normally to a point where it isthe same as that of the atmosphere surrounding it. This process gives agraph which may resemble the graph shown in Figure 3. If the vessel orarea treated was not covered in its entirety with the one treatment,then the above procedure is repeated into the untreated area whileallowing a three inch overlap of the Winding into the area alreadytreated and when the end is reached the windings may be removed. Withthe present invention, the metal being treated may be annealedthoroughly and efliciently as though it had been removed and heattreated in a furnace. As above stated, with the present invention theobject being treated need not be disturbed from its normal operatingposition.

I claim:

1. In combination, a metal member to be heat treated in situ, aplurality of insulated blocks arranged in end to end spaced apartrelation with respect to each other and said blocks being arrangedcontiguous to the outer surface of said member, there being a pair ofspaced parallel longitudinally extending recesses arranged in each ofsaid blocks defining a longitudinally extending partition therebetween,bus bars secured within said recesses, terminals extending outwardlyfrom said bus bars, certain of said terminals adapted to be connected towelding machines, conductors connected to the other of said terminalsand trained around said member, and contacts arranged contiguous to themember being treated and adapted to be connected to a thermocouplepyrometer.

2. In combination, a plurality of insulated blocks arranged in end toend spaced apart relation with respect to each other, there being a pairof spaced parallel longitudinally extending recesses arranged in each ofsaid blocks defining a longitudinally extending partition therebetween,bus bars secured within said recesses, terminals extending outwardlyfrom said bus bars, certain of said terminals adapted to be connected towelding machines, conductors connected to the other of said terminals,and contacts adapted to be connected to a thermocouple pyrometer.

3. In combination, a plurality of insulated blocks arranged in end toend spaced apart relation with respect to each other, there being a pairof spaced parallel longi- 5 tudinally extending recesses arranged ineach of said blocks defining a longitudinally extending partitiontherebetween, bus bars secured within said recesses, terminals extendingoutwardly from said bus bars, certain of said terminals adapted to beconnected to welding machines, conductors connected to the other of saidterminals, and contacts adapted to be connected to a thermocouplepyrometer, said conductors including wires, and a plurality of sphericalbody members mounted on said wires.

4. In combination, a plurality of insulated blocks ar- 10 ranged in endto end spaced apart relation with respect to each other, there being apair of spaced parallel longitudinally extending recesses arranged ineach of said blocks defining a longitudinally extending partitiontherebetween, bus bars secured within said recesses, terminals extendingoutwardly from said bus bars, certain of said terminals adapted to beconnected to welding machines, conductors connected to the other of saidterminals, and contacts adapted to be connected to a thermocouplepyrometer, said conductors including wires, and insulated supportmembers provided with slots for receiving portions of said wires.

References Cited in the file of this patent UNITED STATES PATENTS430,838 Dewey June 24, 1890 1,269,052 Clark et a1 June 11, 19182,044,734 Newhouse June 16, 1936 2,276,643 Bates Mar. 17, 1942 2,319,482Tucker May 18, 1943 2,639,363 Brister et al May 19, 1953 FOREIGN PATENTS135,315 Australia Nov. 15, 1949

